Aerospace structures must have both high performance (i.e., structural stiffness and strength) and low mass. These demanding requirements inherently conflict, and are made even more challenging in that separate subcomponents often must be connected together to create larger structures. Ideally, interfaces or joints would also have the same high performance and low mass as the structural components that are being assembled. In addition, the forces and moments that are transferred across the joints are rarely uniaxial, and are quite commonly a combination of loads applied along different axes.
An example of a prior art structural joint is provided in U.S. Pat. No. 6,379,763 to Fillman. Fillman provides a joint having an elongate cylindrical body with smooth-edged, substantially sinusoidal undulations. The body is enveloped in a sleeve. In order to prevent rotation between the body and the sleeve, the smooth-edged, substantially sinusoidal undulations are interrupted with flats which engage with the sleeve.
Another example of a prior art structural joint is provided in U.S. Pat. No. 7,419,435 to Borges. Borges provides non-round geometries at the ends of the body with a flat neck between the non-round ends which provides a step geometric change along the length of the body. Each non-round cross-section is continuous in Borges, but the 2nd derivatives are not continuous for the axial curves.
Efficiency of a joint is maximized when the part-part load transfer is continuous along the length of the joint. Bolted, pinned and/or riveted joints have disproportionately high load transfer at the first axial row of fasteners. Glued joints transfer most of the load at the two ends of the joint. As discussed above, the prior art has geometric discontinuities (cusp or step geometric changes) which concentrate load transfer in a highly localized manner in the vicinity of the discontinuities.
A structural joint is provided herein which provides improvements to existing joints and which overcomes the disadvantages presented by the prior art. Other features and advantages will become apparent upon a reading of the attached specification, in combination with a study of the drawings.